LTspice IV report component failure?

Discussion in 'General Electronics Chat' started by GregJ7, Sep 3, 2015.

  1. GregJ7

    Thread Starter New Member

    Jun 7, 2014
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    Is there a way to get LTspice to report component failure? The 500kV sine wave I just ran through a small electrolytic capacitor, with the polarity wrong, probably isn't going to produce the nice 500kV sine wave as output that I was shown. The error log didn't say anything. What I am really trying to do is find out when I have messed up a circuit, rather than discover that after I breadboard it. Or possibly worse, when my circuit works, but has a short lifespan. For most situations I suspect it would good enough if LTspice would report when I have used a component out of spec.
     
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  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    What you are describing seems to be a shortcoming with most (perhaps all) simulation engines --- FWIW: Similar annoyances include the assumptions that all reverse biased semiconductor junctions (with the exception of Zeners) and, for that matter, all insulators (including air) exhibit infinite breakdown EMFs --- All conductors exhibit zero resistance (and, hence, infinite current handling capability) -- All resistors exhibit infinite power handling ability --- 'lossy' dielectric and magnetic phenomenon are not 'accounted for', etc...:rolleyes:

    But to answer your question -- I would model a gas discharge tube with appropriate 'strike' (i.e. breakdown) EMF and infinite hysteresis then place same in parallel with the Cap (while the resultant failure mode would present, perhaps unrealistically, as an abrupt, persistent, low impedance condition - you should be alerted to the failure--- Mind you I'm no expert where simulators are concerned!:oops:

    Agreed! It really doesn't seem too much to ask does it?!:mad: -- Especially as such abuse is often less than obvious --- as regards, for instance, switching transients, resonant circuits, etc...)

    Hope to have been of some assistance:)

    Best regards
    HP
     
    Last edited: Sep 3, 2015
  3. crutschow

    Expert

    Mar 14, 2008
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    There was (is) a Spice simulator called Analog Workbench (different from Electronic Workbench) which monitored peak, average and RMS stress levels for conditions such as overvoltage, power dissipation, secondary breakdown, junction temperature and others. It showed a "Smoke Alarm" icon if any of those limits were exceeded.
    It may still be sold by Cadence but I'm not sure how up-to-date that website is.

    But to do that, the simulator must have all the maximum voltage, power, safe-area information, etc. in its library and that's not a part of the normal Spice models. It would have to be added in as separate information. And, of course, some of the limits, like power, can depend upon the device case style and whether it's on a heatsink.

    I use LTspice and look at the circuit for parts that would likely be stressed due to high voltage, current, or power, and then display those part's simulation results.
    For example you can do a Transient Analysis and then if you ALT/Left Click on a part, it will plot the instantaneous power for that device over the transient period.
    If you then CTL/Left Click on the label for that plot, it will show the average power for the transient period.

    Sometimes you have to do a little work to get the info you want. The computer can't always do it all. :rolleyes:
     
    Last edited: Sep 3, 2015
  4. GregJ7

    Thread Starter New Member

    Jun 7, 2014
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    Well, SPICE was invented before MS-DOS and look at the mess we have today with its children. More frighteningly, you're implying that circuit simulators that cost as much as a small house still don't do this. Hopefully the shame of the presidents of companies that develop simulators will reach a point where they will bite the bullet and create a new modeling format (and if it is a large company, recreate component data for everything in the world, although that would be silly since crowdsourcing would be perfect for that).
     
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  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    There you go. your chance to become rich, rich, rich.:cool:
    If at each time step it had to check all those parameters it might take a lot of compute power.
     
  6. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    I dunno -- it could compare maximum attained quantities to maximum component specifications following each run/iteration... --- In any event the feature would (should) be optional... --- My $0.02

    Best regards
    HP:)
     
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